With the gas cylinder being swaged it could have only been made by Inland, Rock Ola, Buffalo Arms, Saginaw or Brown Lipe Chapin (BI).
I don't recall how post war SA barrels were done.

It's just something about the style/shape of that cylinder and the way it butts againt the under flat/slide grooves area.

Can't recall the CC NL that had info about the shape of real cylinders vs fake ones. I'll look later but at this time I don't believe this is a real GI barrel.

My thoughts.. this one may very well be one of those Kahr Arms/ Auto Ordnance barrels that were being offered up with some having fake maker stamps a few years ago.

To the OP:
Hang tight someone will nail it down.

Tough way to welcome a new member, but we keep the door open

Regards
Charlie-Painter777